Image forming apparatus with highly operable sheet discharge device

ABSTRACT

An image forming system includes a digital copy machine to form an image on a group of sheets from an image of a group of documents, and a staple sorter sorting and discharging copied sheets from the digital copy machine. According to the staple sorter, control is provided so that a sheet of a long left period of time is transported from the bin to a nonsort tray when all of a plurality of bins provided in the staple sorter are used during a print operation. The left time of a sheet is monitored even when a print operation is not carried out. When the left time exceeds a predetermined time, control is provided so that the sheet left in the bin is transferred to the nonsort tray. As a result, a sheet discharge device is provided improved in operability of sheet discharge.

[0001] This application is based on Japanese Patent Application Nos.10-107789 and 10-170068 filed in Japan, the contents of which are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to a sheet processing device tosort and discharge a sheet on which an image is formed, and an imageforming system including this sheet processing device and an imageforming apparatus.

[0003] Description of Related Art

[0004] In an image forming apparatus including a conventional sheetprocessing device, there are cases when a plurality of users share oneprinter. In order to prevent a subsequent printed sheet from being mixedup at the sheet discharge unit, a sensor is provided to detect thepresence of a sheet corresponding to each of a plurality of dischargebins to select an appropriate discharge bin to discharge a sheet.

[0005] Such a printer is limited in the number of the discharge bins.When a sheet is discharged and left at all the discharge bins, dischargeof another sheet will cause that sheet to be mixed up with the sheetalready left on any of the discharge bins.

[0006] As an image forming apparatus including such a sheet processingdevice, the technique disclosed in Japanese Patent Laying Open Nos.8-9169, 6-92538, and 8-20457 is known.

[0007] According to the technique disclosed in Japanese PatentLaying-Open No. 8-9169, a sheet will be discharged to a particulardischarge unit when all the discharge bins have sheets output therein.However, the problem of a newly output sheet being mixed up with thesheet left on the discharge bin will not be solved. This is inconvenientfor the user. The operability in discharging a sheet is notsatisfactory.

[0008] According to the technique disclosed in Japanese PatentLaying-Open Nos. 6-92538 and 8-20457, the position of the discharge binis shifted to the left and the right to easily identify the intervalbetween a job (one set of a series of printing process for a group oforiginal documents). However, such a structure will increase the cost,and mixture of the discharge sheets cannot be avoided even when theoutput sheets are shifted and mounted for every job at the dischargebin. Furthermore, the interval between the jobs cannot be easilydetected at a glance even when shifting is carried out on the dischargebins arranged in the vertical direction. This may cause the userinconvenience. The operability in discharging a sheet is not of thesatisfactory level.

[0009] It is to be noted that the capacity of storing sheets in the binof the sheet output device (bin capacity) is limited. The sheet outputmust be suppressed during the operation when the bin capacity has cometo its limit.

[0010] A sheet output device is proposed to continue the sheet output atanother bin when the capacity of the current bin arrives at its limit.When sheets are output into separate plurality of bins, there is apossibility that not all the sheets may be collected. The user mayforget about the other sheets in another bin. There is a problem that,not only the operability of the user specifying the current sheetoutput, but also the operability of other users, will be degraded.

SUMMARY OF THE INVENTION

[0011] In view of the foregoing, an object of the present invention isto provide a sheet processing device improved in operability, connectedto an image forming apparatus.

[0012] Another object of the present invention is to prevent sheetsdischarged corresponding to a plurality of image forming jobs, if any,from being mixed up at the discharge unit in a sheet processing deviceconnected to an image forming apparatus.

[0013] A further object of the present invention is to prevent adischarged sheet of another job from being mixed up when the number ofthe sections where sheets are discharged corresponding to a plurality ofimage forming jobs, if any, is limited and all the sections are occupiedby one job in a sheet processing device connected to an image formingapparatus.

[0014] Still another object of the present invention is to provide asheet processing device improved in operability.

[0015] A still further object of the present invention is to provide animage forming system including an image forming apparatus and a sheetdischarge device connected thereto and improved in operability.

[0016] The above objects can be achieved by a sheet processing devicethat processes a discharge sheet.

[0017] According to an aspect of the present invention, a sheetprocessing device which processes sheets discharged from an imageforming apparatus executing a print job, includes: a first dischargetray; a plurality of second discharge trays; a plurality of sensorswhich detects whether there is a sheet on each of the plurality ofsecond discharge trays, a transport unit which transports a bundle ofsheets from the second discharge tray to the first discharge tray; and acontroller which controls the transport unit so that, when detection ismade of a sheet on all the second discharge trays by the sensor at thetime of discharging a sheet by a new job, at least one of seconddischarge trays is selected according to a predetermined condition totransport a bundle of sheets from the selected second discharge tray.

[0018] When the sensor detects that sheets are discharged at all theplurality of second discharge trays in the event of discharging a sheetaccording to a new process job, a second discharge tray is selectedaccording to a predetermined condition. The sheet already discharged onthe selected second discharge tray is transported onto the firstdischarge tray. The sheet output from the new process job is dischargedonto the second discharge tray from which the sheet has been removed.

[0019] Accordingly, a second discharge tray on which a sheet is notplaced is prearranged. A sheet is discharged corresponding to the newjob onto the prearranged second discharge tray. Therefore, the sheetoutput corresponding to a new job will not be mixed up at the dischargetray. Thus, the operability of the device is improved.

[0020] According to another aspect of the present invention, a sheetprocessing device includes: a first discharge tray; a plurality ofsecond discharge trays; a plurality of timers which count the time of abundle of sheets left on each of the plurality of second dischargetrays; a transport unit which transports the bundle of sheets dischargedon the second discharge tray to the first discharge tray; and acontroller which controls the transport operation of the transport unitaccording to the count result of the timers. The bundle of sheetsdischarged on the second discharge tray is transported to the firstdischarge tray according to the time of the bundle of discharged sheetsleft at the plurality of second discharge trays. As a result, the bundleof sheets left for a long period are discharged to the first dischargetray, and the second discharge tray is prepared for a new job.

[0021] According to a further aspect of the present invention, a sheetprocessing device which processes sheets discharged from an imageforming apparatus that executes a print job, includes: a memory whichstores identification information of a user requesting a jobcorresponding to a plurality of jobs; a first discharge tray; aplurality of second discharge trays; a transport unit which transportsto the first discharge tray a bundle of sheets discharged on the seconddischarge tray; and a controller which controls the transport unit sothat a bundle of sheets of a previous job is transported from a seconddischarge tray when the user of a new job differs from the user of theprevious job at the time of discharging a sheet by the new job to thatsecond discharge tray from which the sheet of the previous job has beendischarged.

[0022] When a sheet according to a newly processed job is to bedischarged onto a second discharge tray in which a sheet is alreadydischarged according to the detection by the sensor, the sheet accordingto the newly processed job is discharged onto the second discharge trayon which a sheet is already discharged when the user processing the newjob is the same user processing the previous job corresponding to thesheet already discharged on the second discharge tray, and the sheetalready discharged on the second discharge tray is transported to thefirst discharge tray so that the sheet according to the newly processedjob is discharged onto that second discharge tray from which the sheethas been removed by the transportation when the user processing the newjob differs from the user processing the previous job corresponding tothe sheet already discharged on the second discharge tray.

[0023] Thus, a second discharge tray on which no sheet is placed isprearranged. A sheet corresponding to a new job is discharged onto theprearranged second discharge tray. The sheet output corresponding to thenew job will not be mixed up at the discharge sheet unit. Thus, theoperability of the device is improved.

[0024] According to still another aspect of the present invention, asheet processing apparatus includes: a first discharge tray; a pluralityof second discharge trays; a detector which detects a state that a sheetcannot be discharged to at least one of the plurality of seconddischarge trays; a transport unit which transports a bundle of sheetsdischarged on the second discharge tray to the first discharge tray; anda controller which controls the transport operation of the transportunit according to a detect result of the detector.

[0025] Detection such as capacity overflow is made for at least one ofthe plurality of second discharge trays. A sheet is transported to thefirst discharge tray according to the detection. Thus, a sheetprocessing device improved in operability can be provided.

[0026] The foregoing and other objects, features, aspects and advantagesof the present invention will become more apparent from the followingdetailed description of the present invention when taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027]FIG. 1 schematically shows an entire structure of an image formingsystem including a staple sorter and a digital copy machine connected tothe staple sorter according to a first embodiment of the presentinvention.

[0028]FIG. 2 is a schematic sectional view of a structure of a digitalcopy machine.

[0029]FIG. 3 is a plan view of a structure of an operation panel 150provided at a top plane of a digital copy machine.

[0030]FIG. 4 is a diagram to describe a structure of a staple sorter.

[0031]FIGS. 5, 6, 7, 8, 9 and 10 are diagrams to describe the movementof a sheet bundle transport gate in a staple sorter.

[0032]FIG. 11 is a block diagram showing a structure of a control unitcontrolling a digital copy machine and a staple sorter connected to thedigital copy machine.

[0033]FIG. 12 shows a bin information management table stored in a RAM.

[0034]FIG. 13 is a flow chart showing the control procedure of a CPU ata staple sorter.

[0035]FIG. 14 shows a user information management table stored in a RAMproduced by the CPU that controls a staple sorter of an image formingsystem according to a second embodiment of the present invention.

[0036]FIG. 15 shows a bin information management table stored in a RAMproduced by the CPU that controls the staple sorter.

[0037]FIG. 16 is a flow chart showing the control procedure at the CPUthat controls the staple sorter.

[0038]FIGS. 17, 18, 19, 20, 21, 22, 23, 24 and 25 are flow chartsshowing a select process A, B, C, D, E, F, G, H and I, respectively, ofa bin for stacking.

[0039]FIG. 26 shows a user information management table stored in a RAMproduced by the CPU that controls a staple sorter of an image formingsystem according to a third embodiment of the present invention.

[0040]FIG. 27 is a flow chart showing a control procedure of the CPUthat controls the staple sorter.

[0041]FIG. 28 specifically shows a bin information management tableaccording to a fourth embodiment of the present invention.

[0042]FIGS. 29A and 29B are flow charts of the process of the CPU of thefourth embodiment.

[0043]FIG. 30 is a flow chart showing a subroutine of a stack process inthe fourth embodiment.

[0044]FIG. 31 is a diagram to describe a mechanism of shifting a nonsorttray.

[0045]FIG. 32 shows a shifted state of the nonsort tray.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] An image forming system including a staple sorter and a digitalcopy machine connected to the staple sorter according to embodiments ofthe present invention will be described hereinafter with reference tothe drawings.

First Embodiment

[0047]FIG. 1 is a diagram to describe an entire structure of an imageforming system including a staple sorter 10 and a digital copy machine200 connected to staple sorter 10 according to a first embodiment of thepresent invention.

[0048] In digital copy machine 200, an operation of a user is input viaan operation panel 150 (refer to FIGS. 2 and 3) in forming an image. Inresponse to a user input, a circulation type automatic documenttransport device 500 mounted on digital copy machine 200 feeds out onedocument at a time of one group of documents placed on a predetermineddocument supply tray onto a glass platen. When an exposure process isapplied on the document on the glass platen, document transport device500 discharges the document on the platen glass sequentially onto adocument discharge tray.

[0049] As shown in FIG. 2, digital copy machine 200 forms an image on asheet from the image of a document read by an exposure process accordingto electrophotography. The sheet on which an image is formed istransferred to staple sorter 10 to be discharged on a nonsort tray 20 ofstaple sorter 10 or on a discharge bin of a bin assembly 30.

[0050] Referring to FIG. 2, digital copy machine 200 is constitutedmainly by an automatic document transport device 500 transporting adocument and inverting the front and back side of a document, ifnecessary, a reader IR reading out an image of a document to generateimage data, a memory unit 230 temporarily storing image data obtained byreader IR, a printer device PRT printing out on a copy sheet accordingto the image data stored in memory unit 230, an operation panel 150(provided at the top plane of digital copy machine 200 (verticaldirection in the drawing) to enter an operation, and an externalinput/output control unit 250 to input/output data.

[0051] When a print operation is designated at automatic documenttransport device 500, the document set on a document supply tray 501 isset at the readout position on glass platen 215 automatically startingfrom the bottom sheet of documents. When the reading operation by readerIR is completed, the document is discharged on discharge tray 502.

[0052] Reader IR includes a scanning system 210 and an image signalprocessor 220. At scanning system 210, the image of the document set atthe read position is exposed by an exposure lamp 211 attached to ascanner 216 that travels below the document. The reflected light fromthe document passes through a reflection mirror and a condenser lens 212to enter photoelectric conversion elements 213 and 214 employing a CCDarray and the like. The signal obtained by scanning system 210 is sentto image signal processor 220. Image signal processor 220 appliesvarious image processes on the input signal such as binarization,picture quality correction, variable scale magnification, and imageediting. The image data subjected to the image process is stored inmemory unit 230.

[0053] Printer device PRT includes a print processor 240, an opticalsystem 260, an image forming system 270, and a sheet transport system280. Print processor 240 drives optical system 260 according to theimage data from memory unit 230. At optical system 260, semiconductorlasers 261 and 262 emit a laser beam respectively according to thesignal under control of print processor 240. The laser beams arecombined at a dichroic mirror 263 and reflected by a polygon mirror 265that is rotated by a motor 264. The reflected beam passes through a mainlens 266 to be directed to a photoconductor 271 of image forming system270.

[0054] At image forming system 270, photoconductor 271 is charged by acorona charger 272. Then, the laser beam from optical system 260 isdirected thereto. Accordingly, an electrostatic latent image is formedon photoconductor 271. Then, toner is placed on the electrostatic latentimage by a developing device 273. The toner image on photoconductor 271is transferred onto a copy sheet fed from a sheet feed cassette 280 a ora sheet feed cassette 280 b of sheet transport system 280. The sheet isthen delivered to a fixer 282 by a sheet feed transport belt 281. Thetoner is fixed on the sheet by heat and pressure. Then, the sheet isdischarged towards a pair of input rollers 81 of staple sorter 10 (referto FIG. 4) connected to digital copy machine 200.

[0055] External input/output control unit 250 transfers data between alocal network (LAN) and a public telephone line (PSTN). Externalinput/output control unit 250 includes a facsimile converter totransmit/receive data to/from memory unit 230 in a facsimile operationmode to carry out conversion of the pixel density, coding method and thelike, a G3 unit providing communication control such as modulation anddemodulation of image data and control signals in a facsimile operationmode and also connected to a telephone line for communication controlwith a PSTN, and a network controller connected to a LAN to providenetwork control for transferring control signals and image data with anexternal device connected to the LAN.

[0056]FIG. 3 is a plan view to describe the structure of operation panel150 on the top plane of digital copy machine 200.

[0057] Operation panel 150 includes a touch panel 151 on which the copycondition and the internal status of digital copy machine 200 aredisplayed by liquid crystal, and through which a predetermined operationcan be input to set the copy condition and the like, a ten key 152 toinput numerics of the number of copies, the copy scale rate and thelike, a reset key 153 to reset the copy condition specified by the user,an interrupt key 154 to interrupt the current process, and a start key155 to designate initiation of the copy operation.

[0058]FIG. 4 is a diagram to describe the internal structure of staplesorter 10.

[0059] Staple sorter 10 includes a sheet transport unit 80, a binassembly 30 of five stages of discharge bins 311-315 (referred to asbins 315-335 hereinafter), a staple unit 70 for stapling a bundle ofsheets, if necessary, a remove unit 40 driven by a motor M70 to deliverthe bundle of sheets on bins 311-315 to a sheet bundle transport gate100 for removal, a nonsort tray 20, and sheet bundle transport gate 100transporting the bundle of sheets removed from bins 311-315 by removeunit 40 onto nonsort tray 20.

[0060] The following description is mainly focused on sheet transportunit 80, bin assembly 30, staple unit 70 and sheet bundle transport gate100 with reference to FIG. 4.

[0061] Sheet transport unit 80 includes a roller pair 81 to receive asheet discharged from digital copy machine 200 (refer to FIG. 1), afirst transport unit 83 to transport a sheet in substantially a verticaldirection, a switching claw 82 to switch the sheet transport directiontowards first transport unit 83 or sheet bundle transport gate 100, anda second transport unit 90 to transport the sheet from first transportunit 80 towards bin assembly 30 in a substantially horizontal direction.

[0062] Here, switching claw 82 can be made to rotate about a supportshaft 82 a according to the ON/OFF of a solenoid SL50.

[0063] When solenoid SL50 is off, switching claw 82 is set at theposition shown in FIG. 4. In this case, the sheet discharged fromdigital copy machine 20 and received by input roller pair 81 is guidedby the curved right surface of switching claw 82 to be sent to firsttransport unit 83.

[0064] When solenoid SL50 is on, switching claw 82 rotates clockwisefrom the position shown in FIG. 4. In this case, the sheet dischargedfrom digital copy machine 200 and received by roller pair 81 is guidedon the upper surface of switching claw 82 by a guide plate 79 to betransported to nonsort tray 20 through sheet bundle transport gate 100.

[0065] First transport unit 83 includes guide plates 84-87 to guide thesheet, transport roller pairs 88 and 89 to transport a sheet. A punchunit 75 is arranged at the middle stage portion to form a binding holeat the leading end or trailing end in the transportation direction ofthe sheet. Second transport unit 90 includes a pair of transport rollers91 and 92 to transport a sheet, and guide plates 93 and 94 to guide asheet. Guide plate 94 is attached to the side plate portion of guideplate 93. Transport roller 91 is attached to one end of guide plate 94.Second transport unit 90 can be moved about a support shaft 95approximately 90° in the direction of arrow a from the position shown inFIG. 4.

[0066] In staple sorter 10, second transport unit 90 takes the positionshown in FIG. 4 when sheets are distributed towards bins 311-315. Thesheet delivered from first transport unit 83 by transport rollers 91 and92 is sent towards bin assembly 30. Second transport unit 90 rotatessubstantially 90° in the direction of arrow a about support shaft 95 tobe withdrawn from the sheet transport position when a bundle of sheetsfrom bins 315-316 are to be output on nonsort tray 20.

[0067] A sensor SE21 is arranged at second transport unit 90. SensorSE21 senses the sheet stored in bins 311-315 and the bundle of sheetsremoved from bins 311-315.

[0068] Input roller pair 81, transport roller pairs 88 and 89, transportrollers 91 and 92, and remove rollers 42 and 43 of remove unit 40 todeliver the bundle of sheets to sheet bundle transport gate 100 inremoving the bundle of sheets from bins 311-315 are rotated by a drivingforce transmission means not shown by a motor M50.

[0069] Bin assembly 30 includes five stages of bins 311-315. Each ofbins 311-315 is arranged at a constant interval in a slanted manner. Apin 32 provided at the lower end side of each of bins 311-315 engageswith a spiral groove formed at the outer perimeter of a drive shaft notshown provided in the vertical direction. The drive shaft is rotated inone direction or the opposite direction by a motor M60 to raise/lowereach of bins 311-315.

[0070] Bin assembly takes the home position shown in FIG. 4. In thishome position, first bin 311 faces transport rollers 91 and 92. Secondbin 312 faces staple unit 70. The position of bins 311-315 correspondingto transport rollers 91 and 92 is referred to as position X1hereinafter. The position of bins 311-315 corresponding to staple unit70 is referred to as position X2 hereinafter.

[0071] When the drive shaft is contrarotated once from the state wherefirst bin 311 takes position X1, first bin 311 is lowered to position X2and second bin 312 is lowered to the position in contact with third bin313. The bundle of sheets on first bin 311 can be bound by staple unit70 when first bin 311 takes position X2. When the drive shaft is rotatedonce in the positive direction after the bundle of sheets are stapled,first bin 311 is elevated to position X1 and second bin 312 is elevatedto position X2. The stapled sheets on first bin 311 are removed by theuser with first bin 311 at position X1.

[0072] Bin assembly 30 is provided with a sensor (not shown) to detectthat each of bins 311-315 is set at the home position, and a sensor (notshown) to detect that each of bins 311-315 is elevated by one pitch atone turn of the drive shaft. Sensors SE341-S345 are attached to each ofbins 311-315 to detect the presence of a sheet.

[0073] At staple sorter 10 of the present embodiment, the position ofdistributing sheets to each of bins 311-315 and the position of removinga bundle of sheets are both the same position X1. The structure of thesorter unit is simplified by carrying out the storage and removal of asheet at the same position.

[0074] Staple unit 70 is formed of the well known motor-operatedstructure. Staple unit 70 includes a head unit 71 with a detachablecartridge in which staples are set, and an anvil unit 72 to receive andbend a staple output from head unit 71. Staple unit 70 is moved towardsbins 311-315 set at position X2 to drive in a staple at one corner ortwo staples at the end portion of a bundle of sheets.

[0075] Staple unit 70 can move towards the rear side with the front sideof staple sorter 10 (the front side of the drawing) as the homeposition. Staple unit 70 temporarily stops at a predetermined positionand then moves towards bins 311-315 to drive in a staple. Staple unit 70returns to the home position following the drive-in of a staple. A notchis formed at the lower end portion of each of bins 311-315 where astaple is to be driven in, whereby the leading end of staple unit 70 canenter the bin side.

[0076] Sheet bundle transport gate 100 includes a pair of gate rollers102 and 103 in a box 101, and sheet guide plates 104 and 105. Rollers102 and 103 are rotated clockwise/counterclockwise by a motor M21. Sheetbundle transport gate 100 is guided by a guide member not shown to beelevated/lowered. A motor M20 is provided as a driving source thereof.

[0077] Sheet bundle transport gate 100 takes the home position shown inFIG. 4. At the home position, sheet bundle transport gate 100 deliversleftward in FIG. 4 a sheet guided on the top plane of switching claw 82from roller pair 81 by means of rotation of rollers 102 and 103 towardsnonsort tray 20.

[0078] Sheet bundle transport gate 100 can be shifted within staplesorter 10 as shown in FIGS. 5-10. FIGS. 5-10 are diagrams to describethe movement of sheet bundle transport gate 100 within staple sorter 10.

[0079] Sheet bundle transport gate 100 is lowered down to the positionfacing bin 312 set at position X2 (refer to FIG. 5) to receive a bundleof sheets that are stapled/not stapled on bin 312. At this removeposition, sheet bundle transport gate 100 sandwiches a bundle of sheetsS by means of rollers 102 and 103 (refer to FIG. 6) output from bin 312by the shift of remove rollers 42 and 43 of FIG. 4. Sheet bundle S isreceived by sheet bundle transport gate 100 by the positive rotation ofrollers 102 and 103 (refer to FIG. 7).

[0080] Upon complete input of sheet bundle S in sheet bundle transportgate 100, the positive rotation of rollers 102 and 103 stops. At thesame time, sheet bundle transport gate 100 is elevated (refer to FIG.8). When sheet bundle transport gate 100 rises to a predeterminedheight, rollers 102 and 103 contrarotate to discharge the sandwichedsheet bundle S on nonsort tray 20 (refer to FIG. 9). Then, sheet bundletransport gate 100 is raised one pitch and lowered down to the removeposition facing bin 313 set at position X1 (refer to FIG. 10). Astacking operation to nonsort tray 20 can be repeated as describedabove.

[0081] To enable the stacking operation, a sensor SE33 to detectpresence of a sheet on nonsort tray 20 and a sensor SE23 to detect thetop most surface of the sheets on nonsort tray 20 (the upper surface ofnonsort tray 20 when there is no sheet) above nonsort tray 20 as shownin FIG. 4. Also are provided a sensor SE20 to detect that sheet bundletransport gate 100 is at the home position and a sensor SE22 to detectpresence of a bundle of sheet within sheet bundle transport gate 100.

[0082] The stacking operation can be carried out concurrently with thestaple process on the bundle of sheets on the bin set at position X2 instaple sorter 10.

[0083] Digital copy machine 200 and staple sorter 10 of the abovestructure are under control of the control unit shown in FIG. 11.

[0084]FIG. 11 is a block diagram showing a structure of the control unitproviding control of digital copy machine 200 and staple sorter 10connected to digital copy machine 200.

[0085] The control unit includes a ROM 171 storing a program to operatestaple sorter 10, a CPU 170 executing a program, a RAM 172 storinginformation required for program execution, and a CPU 173 controllingdigital copy machine 200.

[0086] Various detection signals from sensor SE20 detecting that sheetbundle transport gate 100 is at the home position, sensor SE21 detectingpresence of a bundle of sheets at second transport unit 90, sensor SE22detecting presence of a bundle of sheets within sheet bundle transportgate 100, sensor SE23 detecting the top most face of the sheets onnonsort tray 20, sensor SE33 detecting presence of sheet on nonsort tray20, and sensors SE341-SE345 detecting presence of a sheet on each ofbins 311-315, respectively, shown in FIG. 4, are applied to CPU 170.

[0087] CPU 170 outputs respective drive signals to motor M20 movingsheet bundle transport gate 100 in the vertical direction, motor M21 torotate rollers 102 and 103 in sheet bundle transport gate 100, motor M50to drive various rollers in staple sorter 10, motor M60 to drive a shaftthat moves each of bins 311-315 in the vertical direction, motor M70 todrive remove unit 40, and solenoid SL50 to drive switching claw 82 thatswitches the sheet transport direction.

[0088] A CPU 173 providing the control of various components (refer toFIG. 2) of reader IR of digital copy machine 200, memory unit 230,printer device PRT and operation panel 150 is connected to CPU 170. Asignal requesting initiation of a print process is sent from CPU 170 toCPU 173. A signal indicating the end of a printing process is sent fromCPU 173 to CPU 170. Signals are transferred between CPU 173 and CPU 170to carry out a process at staple sorter 10 while adjusting the printingtiming of an image onto a sheet at digital copy machine 200.

[0089] CPU 170 includes an internal counter to count the period of timeof a sheet left on each bin.

[0090] According to staple sorter 10 of the above structure, a bininformation management table as shown in FIG. 12 is generated by CPU 170to be stored in RAM 172. Control according to the flow chart shown inFIG. 13 is provided using the bin information management table stored inRAM 172.

[0091] Referring to the bin information management table of FIG. 12,“bins 1-5” correspond to bins 311-315 (refer to FIG. 4), respectively.Detection is made whether a sheet is discharged at each of bins 1-5 bysensors SE341-SE345. The detected result is “present” and “none” of adischarged sheet. The “left time” indicates the period of time of eachsheet left at bins 1-5. “User” indicates the user using respective bins1-5. The user of bins 1-5 is identified by an ID card and the like thatis inserted into a predetermined slot in which magnetic information isstored.

[0092] For example, it is appreciated that the sheet for the user ofuser ID3 is discharged and left for 3600 seconds on bin 3, according tothe bin information management table.

[0093]FIG. 13 shows a flow chart of the control procedure of CPU 170(refer to FIG. 11) at staple sorter 10 (refer to FIG. 4).

[0094] When the power is turned on to start the program, the bininformation is first checked by staple sorter 10 at step 1 (“step”abbreviated as S hereinafter) to generate a bin information managementtable as shown in FIG. 12. At S2, determination is made whether a printprocess request is detected from CPU 173 controlling digital copymachine 200.

[0095] When a print process request is detected (YES at S2), controlproceeds to S3 to detect whether there is an empty bin (an unused bin)according to the bin information management table.

[0096] When there is no empty bin (NO at S3), control proceeds to S4 toidentify the bin corresponding to the greatest timer value indicatingthe left time according to the bin information control table. The sheetdischarged on the identified bin is delivered onto nonsort tray 20, asshown in FIGS. 510 (stack operation). At S5, determination is made thestacking operation has ended or not. When the stacking operation has notyet ended (NO at S5), control remains at S5. When the stacking operationhas ended (YES at S5), control proceeds to S6 to select the availablebin emptied by the stack operation. A print process initiate requestsignal is sent to CPU 173 that controls digital copy machine 200.Accordingly, the sheet subjected to a printing process is dischargedonto the available bin emptied by the stack operation of staple sorter10.

[0097] At S7, determination is made whether the print operation hasended or not. If the print process has not yet ended (NO at S7), thecontrol remains at S7. When the print process has ended (YES at S7),control proceeds to S8 to initiate the timer counting of the bincorresponding to the ended print process. When the processes arecompleted, control returns to S1.

[0098] When there is an empty bin (YES at S3), control proceeds directlyto S6, skipping the processes of S4 and S5. The bin determined to beempty at S3 is selected, and a print process initiated.

[0099] When a print process request is not detected (NO at S2), controlproceeds to S9 to determine whether there is a bin having a timer valueexceeding a predetermined time indicating the left time according to thebin information management table. When there is no bin corresponding toa timer value exceeding the predetermined time (NO at S9), controlreturns to S1. When there is a bin having a timer value exceeding thepredetermined time (YES at S9), control proceeds to S10 to initiate astack operation for the sheet on that bin. At S11, determination is madewhether the stack operation has ended or not. When the stack operationhas not yet ended (NO at S11), control remains at S11. When the stackoperation has ended (YES at S11), control returns to S1.

[0100] Thus, sensors SE341-SE345 detecting the presence of a sheet ateach of bins 311-315 are provided, and the period of time of the sheetleft on each of bins 311-315 is counted. According to the counted time,the sheet on one of bins 311-315 with the longest left time is conveyedto nonsort tray 20 when all bins 311-315 are used in the event of aprint operation. The left time of a sheet is monitored even whenprinting is not carried out. When the left time exceeds a predeterminedtime, the sheet on the bin corresponding to the value with the exceededpredetermined time is transferred to nonsort tray 20.

[0101] Thus, a bin on which a sheet is not placed is prearranged. Asheet corresponding to a new job is discharged on the prearranged bin.Therefore, the sheet output corresponding to the new job will not bemixed up in that the discharge unit. Thus, the user operability isimproved.

Second Embodiment

[0102] An image forming system according to a second embodiment of thepresent invention will be described hereinafter. The image formingsystem of the second embodiment differs from the image forming system ofthe first embodiment in the control procedure of the staple sorterdescribed with reference to FIGS. 12 and 13. The remaining elements aresimilar to those of the image forming system of the first embodiment.

[0103] According to the staple sorter of the image forming system of thesecond embodiment, a user information management table and a bininformation management table shown in FIGS. 14 and 15 are generated bythe CPU that controls the staple sorter. The tables are stored in theRAM connected to this CPU. Control according to the flow chart of themain routine of FIG. 16 and the flow chart of the subroutine shown inany of FIGS. 17-26 are executed using the user information managementtable and bin information management table.

[0104]FIG. 14 shows a user information control table formed by the CPUproviding control of the staple sorter of the image forming system ofthe second embodiment and stored in a RAM. FIG. 15 shows a bininformation management table generated by the CPU providing the controlof the staple sorter and stored in a RAM.

[0105] Referring to the user information management table of FIG. 14,“priority” is assigned to a “user ID”. A user ID is identified by an IDcard and the like that is recorded with magnetic information and that isinserted into a predetermined insert slot, likewise the image formingsystem of the first embodiment. According to the user informationmanagement table, user ID3 has a priority of 2, which is higher in levelthan the priority of 1 for user ID5. The user priority of user ID3 isset lower than the user priority of user ID5.

[0106] The bin information management table of FIG. 15 is createdaccording to the detected values of respective sensors and the inputcopy condition with respect to a job from the operation panel. “Bins1-5” identify a plurality of bins provided at the staple sorter, such asthe above bins 311-315. “Present” and “none” of the “presence of sheet”indicates whether a sheet is discharged in each of bins 1-5. “Sheetsize” indicates the size of a sheet discharged at each of bins 1-5.“Output number” indicates the number of sheets discharged at each ofbins 1-5. “Job ID” indicates which job relates to the sheets dischargedat each of bins 1-5. “User ID” indicates the user corresponding to thesheet discharged at each of bins 1-5.

[0107] For example, twenty sheets of A4Y in size (T indicates that thelonger side of a rectangular sheet is placed parallel to the sheettransport direction; Y indicates that the longer side of a rectangularsheet is placed perpendicular to the sheet transport direction), notstapled, are discharged on bin 2 by the bin information managementtable. The user ID corresponding to this sheet is 1, likewise to thesheet discharged on bin 1. Also, the user ID corresponding to this sheetis 1, likewise the sheets discharged on bins 1 and 4.

[0108]FIG. 16 is a flow chart showing the control procedure by the CPUproviding control of the staple sorter.

[0109] When the power is turned on to start the program, the userinformation or the bin information is checked at S101 by the staplesorter. The user information management table and bin informationmanagement table as shown in FIGS. 14 and 15 are produced. At 102,determination is made whether a print process request is detected fromthe CPU providing control of the digital copy machine to which thestaple sorter is connected.

[0110] When a print process request is not detected (NO at S102),control proceeds to S101. When a print process request is detected (YESat S102), control proceeds to S103 to determine whether there is anempty bin according to the bin information management table.

[0111] When there is no empty bin (NO at S103), control proceeds toS104. A stack object bin select process to select a bin that is subjectto a stack operation is carried out by the subroutine shown in FIGS.17-26. At S105, determination is made whether there is a bin relevant tothe bin of interest selected at S104.

[0112] When there is no relevant bin (NO at S105), control proceeds toS101. When there is a relevant bin (YES at S 105), control proceeds toS106 to select the relevant bin. Then, a stack operation is initiated.At S107, determination is made whether the stack operation has ended ornot. When the stack operation has not yet ended (NO at S107), controlremains at S107. When the stack operation has ended (YES at S107),control proceeds to S108 to select the available bin emptied by thestack operation. A signal requesting the start of a print process issent to the CPU providing control of the copy machine. Accordingly, asheet subjected to a print process is discharged on the available binemptied by the stack operation by the staple sorter. Then, controlreturns to S101.

[0113] When there is an empty bin (YES at S103), control proceedsdirectly to S108, skipping the processes of S104-S107. The bindetermined to be empty at S103 is selected, and a print operation isinitiated.

[0114] The stack object bin select process of S104 of FIG. 16 will bedescribed with reference to FIGS. 17-26. Although description isprovided of a control using any one of the processes of FIGS. 17-26, aplurality of the processes of FIGS. 17-26 can be combined. Respectivestack object bin select processes of FIGS. 17-26 are denoted asprocesses A, B,. to identify each stack object bin select process.

[0115]FIG. 17 is a flow chart of a stack object bin select process A.The bin on which a sheet is discharged corresponding to the job of theuser with the highest priority is selected as the bin of the subject ofthe stack operation.

[0116] At S1041 a, the job of the user with the highest priority isdetermined according to the user information management table (refer toFIG. 14). At S1042 a, the bin corresponding to the job determined atS1041 a is selected as the relevant bin. Then, the present routine ends.

[0117] When there is a bin selected as the relevant bin in stack objectbin select process A, the sheet on that relevant bin is taken as thesubject of the stack operation (S106 of FIG. 16). By setting thepriority of the user ID for the supervisor at a low level, the job ofthe supervisor will not be taken as the object of the stack operation.The sheet discharged on the bin by the job of the supervisor will not betransported to the nonsort tray (refer to FIGS. 5-10). There is no needto sort the sheets discharged in bundles from a plurality of bins.

[0118]FIG. 18 is a flow chart of a stack object bin select process B.The bin on which a sheet is discharged by a job using the greatestnumber of bins is selected as the bin to be subjected to the stackoperation.

[0119] At S1041 b, the job using the greatest number of bins isdetermined according to “job ID” (refer to FIG. 15) in the bininformation management table. At S1042 b, the bin used by the jobdetermined at S1041 b is selected as the relevant bin. Following theseprocesses, the present routine ends.

[0120] When there is a bin selected as the relevant bin in stack objectbin select process B, the sheet on that relevant bin is taken to be theobject of the stack operation (S106 of FIG. 16). By the stack operationwith respect to one job, more bins can be made available.

[0121]FIG. 19 is a flow chart of a stack object bin select process C.Here, the bin on which a sheet is discharged by the user using thegreatest number of bins is selected as the bin to be subjected to astack operation.

[0122] At S1041 c, the user using the greatest number of bins isdetermined according to “user ID” (refer to FIG. 15) in the bininformation management table. Then, the bin used by the user determinedat S1041 c is selected as the relevant bin. Following these processes,the present routine ends.

[0123] When there is a bin selected as the relevant bin in stack objectbin select process C, the sheet on the relevant bin is taken as theobject of a stack operation (S106 of FIG. 16). By the stack operationcorresponding to one user, more bins can be made available.

[0124]FIG. 20 is a flow chart of a stack object bin select process D.The bin located closest to the nonsort tray is selected as the bin to besubjected to a stack operation.

[0125] At S1041 d, the bin closest to the nonsort tray is selected asthe relevant bin. Then, the present routine ends. Here, the nonsort trayis located above or below the bin assembly. The closest bin differsaccording to the position of the nonsort tray.

[0126] When there is a bin selected as the relevant bin in stack objectbin select process D, the sheet on the relevant bin is taken as theobject of a stack operation (S106 of FIG. 16). The time required for astack operation carried out by interrupting a print operation can bereduced.

[0127]FIG. 21 is a flow chart of a stack object bin select process E.Here, the bin storing the greatest number of sheets is selected as thebin subjected to a stack operation.

[0128] At S1041 e, the bin storing the maximum number of sheets isdetermined according to “output number” (refer to FIG. 15) in the bininformation management table. At S1042 e, the bin determined at S1041 eis selected as the relevant bin. Following these processes, the presentroutine ends.

[0129] If there is a bin selected as the relevant bin in stack objectbin select process E, the sheet on the relevant bin is taken as theobject of a stack operation (S106 of FIG. 16). The image forming systemusing this stack object bin select process E can be improved inconvenience by setting beforehand the jobs of the same user to be outputon the same bin.

[0130]FIG. 22 is a flow chart of a stack object bin select process F.The bin storing the least number of sheets is selected as the bin of astack operation.

[0131] At S1041 f, the bin storing the least number of sheets isdetermined according to “output number” (refer to FIG. 15) in the bininformation management table. At S1042 f, the bin determined at S1041 fis selected as the relevant bin. Following these processes, the presentroutine ends.

[0132] If there is a bin selected as the relevant bin in stack objectbin select process F, the sheet on the relevant bin is taken as theobject of the stack operation (S106 of FIG. 16). An image forming systemusing stack object bin select process F is advantageous in the casewhere the remaining capacity of the nonsort tray is small when an emptybin is selected for output irrelevant to the user.

[0133]FIG. 23 is a flow chart showing a stack object bin select processG. As the bin to be subjected to a stack operation, the bin is selectedon which a sheet of the largest size is discharged when no sheet isdischarged on the nonsort tray, and the bin on which a sheet isdischarged of a size smaller than the size of the sheet discharged onthe nonsort tray, if any.

[0134] At S1041 g, determination is made whether there is no sheet onthe nonsort tray. When there is no sheet on the nonsort tray (YES atS1041 g), the bin storing the largest sheet that can be discharged tothe nonsort tray is determined according to “sheet size” (refer to FIG.15) in the bin information management table. When there is a sheet onthe nonsort (NO at S1041 g), the bin storing a sheet of a size smallerthan the size of the sheet already discharged on the nonsort tray isdetermined according to “sheet size” (refer to FIG. 15) in the bininformation management table. Then, the bin determined at S1043 g isselected as the relevant bin. Following these processes, the presentroutine ends.

[0135] When there is a bin selected as the relevant bin in stack objectbin select process G, the sheet on the relevant bin is taken as anobject of the stack operation (S106 of FIG. 16). Here, the sheetstransported onto the nonsort tray are overlaid from a larger to smallersize upwards.

[0136] This facilitates the sorting of each bundle of sheets without anycomplex structure such as shifting the sheets on the nonsort tray.

[0137]FIG. 24 is a flow chart of a stack object bin select process H.Here, the bin storing stapled sheets is selected as the bin to besubjected to a stack operation.

[0138] At S1041 h, determination is made whether any of the plurality ofbins store stapled bundle of sheets according to “Staple State” (referto FIG. 15) in the bin information management table. When there is nobin storing stapled sheets (NO at S1041 h), control proceeds to S1043 hwhere a predetermined bin (for example, the top most bin) is selected asthe relevant bin. Then, the present routine ends. When there is a binstoring stapled sheets (YES at S1041 h), the bin determined at S1042 his selected as the relevant bin. Then, the present routine ends.

[0139] By selecting a bin that stores stapled sheets as the relevant binto be subjected to a stack operation (S106 of FIG. 16) in stack objectbin select process H, the bundle of sheets on the nonsort tray can besorted easily distinguishing between the bundle of sheets without acomplicated structure such as shifting stapled sheets on the nonsorttray.

[0140]FIG. 25 is a flow chart showing a stack bin select process I.Here, the bin of a job using a number of bins identical in number to thebin that will be used by the job predetermined for the next printing isselected as the bin to be subjected to a stack operation.

[0141] At S1041 i, the number of bins to be used by the job in the nextprint operation is determined according to “job ID” (refer to FIG. 15)in the bin information management table. At S1042 i, determination ismade whether there is a job that uses a number of bins identical innumber to the number of bins determined at S1041 i. When there is no jobusing the same number of bins (NO at S1042 i), a predetermined bin (forexample, the top most bin) determined at S1044 i is selected as therelevant pin. Then, the present routine ends. When there is a job usingthe same number of bins (YES at S1042 i), the bin of the job using thesame number of bins is selected as the relevant bin at S1043 i. Then,the present routine ends.

[0142] By selecting the bin corresponding to the job using a number ofbins identical in number to that to be used by the job of the next printoperation for a stack operation (S106 of FIG. 16) in stack object binselect process I, the sheets on the bin least used by the jobs will betransported onto the nonsort tray. The time required for a stackoperation by interrupting a print operation can be reduced.

[0143] By employing stack object bin select processes A-I of FIGS. 17-25for S104 of FIG. 16, the above-described advantages can be achieved.Also, a bin on which a sheet is not placed is prearranged, so that asheet corresponding to a new job can be discharged on the prearrangedbin. The problem of an output sheet corresponding to a new job beingmixed up at the discharge unit is eliminated. The user operability canbe improved.

Third Embodiment

[0144] An image forming system according to a third embodiment of thepresent invention will be described. The image forming system of thethird embodiment differs from the image forming system of the firstembodiment in the control procedure of the staple sorter described withreference to FIGS. 12 and 13, likewise the image forming system of thesecond embodiment. The remaining elements of the third embodiment issimilar to that of the image forming system of the first embodiment.

[0145] According to the staple sorter of the image forming system of thethird embodiment, a user information management table shown in FIG. 26is produced by the CPU controlling the staple sorter. This table isstored in a RAM connected to this CPU. Control according to the flowchart of FIG. 27 is carried out using the table.

[0146] Referring to the user information management table of FIG. 26,“discharge set bin” is specified corresponding to “user ID”. “Dischargeset bin” specifies a plurality of bins provided at the staple sorterssuch as the above bins 311-315, and is fixedly assigned to a user.According to the user information management table, discharge set bin 3is set so as to be shared by the users of user ID2 and user ID3.

[0147] In the present staple sorter, control is executed as set forth inthe following using the user information management table and the userID corresponding to a bin in the bin information management table shownin FIG. 15.

[0148]FIG. 27 is a flow chart showing the control procedure of the CPUcontrolling the present staple sorter.

[0149] When the power is turned on and the program initiated, the userinformation is checked at S201 by the present staple sorter. A userinformation management table as shown in FIG. 26 is generated. At S202,determination is made whether a print process request has been detectedor not from the CPU providing control of the digital copy machine towhich the present staple sorter is connected.

[0150] When a print process request is not detected (NO at S202),control proceeds to S201. When a print process request is detected (YESat S202), control proceeds to S203 to select the bin in which a sheet isdischarged by the user ID according to the user information managementtable (refer to FIG. 26).

[0151] At S204, determination is made whether there is a sheet on thebin selected at S203. When there is a sheet on the selected bin (NO atS204), control proceeds to S205 to detect whether the user ID of theuser corresponding to the selected bin (allocated bin) is identical tothe user ID of the user requesting a print operation.

[0152] When the user ID of the user corresponding to the selected bin isnot identical to the user ID of the user requesting a print operation(NO at S205), control proceeds to S206 to initiate a stack operation forthe sheet placed on the selected bin. At S207, determination is madewhether the stack operation has ended or not. When the stack operationhas not yet ended (NO at S207), control remains at S207. When the stackoperation ends (YES at S207), control proceeds to the process of S208.

[0153] At S208, a signal requesting initiation of a print process issent to the CPU providing control of the digital copy machine. At S209,determination is made whether the print process has ended or not. Whenthe print process has not yet ended (NO at S209), control remains atS209. When the print process ends (YES at S209), control proceeds toS210 to store the user ID of the user using the bin into the bininformation control table. Then, control returns to S201 to initiate theprocess from the beginning.

[0154] When the user ID of the user using the selected bin is identicalto the user ID of the user requesting the print operation (YES at S205),control proceeds to S211 to determine whether a staple process isspecified for the sheet corresponding to the print request. When settingis not made of a staple process (NO at S211), control proceeds to theprint process of S208. When a staple process is set (YES at S211),control proceeds to the select bin stack request of S206.

[0155] When there is no sheet on the selected bin (YES at S204), controlproceeds to the print process of S208.

[0156] Accordingly, when there is no sheet discharged at the binassigned for each user (specified bin) in carrying out a new printoperation, the sheet is discharged to the specified bin. When there is asheet already in the specified bin, the sheet is discharged in anoverlying manner at the specified bin when the sheet already dischargedis of the same user, provided that the sheets are not stapled. When thesheet already discharged is of a different user or when the sheets arestapled, the sheets on the specified bin are transferred to the nonsorttray in a bundle.

[0157] Thus, a bin in which a sheet is not placed is prearranged, and asheet corresponding to a new job is discharged onto the prearranged bin.A sheet discharged corresponding to a new job will not be mixed up atthe discharge unit. Therefore, the operability of the user is improved.

Fourth Embodiment

[0158] According to a fourth embodiment of the present invention, a bininformation management table as shown in FIG. 28 is generated by CPU 170and stored in RAM 172. By using this bin information management table,the ID number of a job corresponding to the sheet output to the bin andcapacity overflow of the bin can be controlled.

[0159] Referring to the bin information management table of FIG. 28,“bins 1-5” correspond to aforementioned bins 311-315 (refer to FIG. 4),respectively. “Nonsort tray” corresponds to nonsort tray 20.

[0160] “Number of sheets” records the total number of sheets placed onnonsort tray 20 and each of bins 311-315.

[0161] “Job ID” stores the ID indicating which job corresponds to thesheet discharged at each of nonsort tray 20 and bins 311-315. Forexample in FIG. 28, the job ID for all of bins 3-5 is “3”. This meansthat the sheets resulting from the execution of a copy operation with asort operation (one job) are output to bins 3-5. Bins 1 and 2 have thejob ID of “1” and “2”, respectively. This indicates that sheetsdischarged by different jobs are placed therein.

[0162]FIGS. 29A and 29B are flow charts showing the control process ofstaple sorter 10 by CPU 170 according to the fourth embodiment.

[0163] Referring to FIGS. 29A and 29B, a display process correspondingto touch panel 151 (refer to FIG. 3) is carried out at S301. The processis carried out of displaying which tray contains the output of the sheetcorresponding to a job carried out by a user, and displaying a messageindicating the divided output of the sheets of one job to nonsort tray20 and bins 311-315.

[0164] At S303, the check and update of the information in the bininformation management table of FIG. 28 are carried out. At S305,determination is made whether a print operation is currently carried outby digital copy machine 200. When NO at S305, control proceeds to S307to determine whether the print end edge is output from CPU 173. Here,the print end edge is a signal output immediately after completion of aprint operation by digital copy machine 200.

[0165] When YES at S307, control proceeds to S309 to determine whetherthe sort mode is selected by the user or not. Here, a sort mode is themode to sort the output by one job into bins 311-315. For example, whenthe user sets a sort mode for one group of documents and “3” as therequired number of copies, three set of copied sheets are distributedinto different bins.

[0166] When YES at S309, control proceeds to S311 to determine whether astack operation for the nonsort tray is possible or not by checking thecolumn of the nonsort tray in the bin information management table. Forexample, S111 provides the determination of NO when the number of sheetsplaced on the nonsort tray exceeds the permitted number of sheets of thenonsort tray.

[0167] When YES at S311, control proceeds to S313 to carry out theprocess of transferring and stacking the group of sheets output frombins 311-315 to nonsort tray 20. Following the process of S313, controlreturns to S301.

[0168] When NO at S309 or S311, control returns to S301.

[0169] When NO at S307, control proceeds to S315 to determine whetherthere is a print request from CPU 173. When YES at S315, the bininformation management table is referred to at S317 to determine whetherthere is an empty bin (a bin having the number of sheets of 0). When YESat S317, control proceeds to S319 to select that empty bin. A printprocess of discharging a sheet to the empty bin is carried out.Following the process of S319, control returns to S101. when NO at S315or S317, control directly returns to S301.

[0170] When YES at S305, control proceeds to S321 to determine whetherthe bin with the sheet output exceeds the capacity or not. Determinationis made by referring to the bin information management table to checkwhether the number of sheets corresponding to that bin has exceeded astandard value or not.

[0171] When YES at S321, control proceeds to S323 to determine whether astack process for nonsort tray 20 is allowed or not.

[0172] When YES at S323, control proceeds to S325 to carry out theprocess of transferring and stacking the bundle of sheets in the bindetermined to have exceeding capacity to nonsort tray 20.

[0173] Following the process of S325, control proceeds to S327 todetermine whether the sort mode is selected or not. When NO at S327,nonsort tray 20 is selected as the output destination of the sheet. Aprinting operation and an output process are resumed. Then, controlreturns to S101.

[0174] When YES at S327, control proceeds to S319 to select an emptybin. Then, a print operation is resumed.

[0175] When NO at S323, control returns to S301.

[0176] When NO at S321, control proceeds to S331 to determine whether asheet that cannot be output to the bin (a sheet outside the outputrange) has been transported or not. When YES at S331, control proceedsto S333 to determine whether a stack process is allowed for nonsort tray20.

[0177] When YES at S333, control proceeds to S335 to carry out theprocess of transferring and stacking the sheets on the bin to nonsorttray 20. At S337, nonsort tray 20 is selected as the output destinationof the sheet. In the subsequent print process, the sheets are output tononsort tray 20. Then, control returns to S301.

[0178] When NO at S331 or S333, control returns to S301.

[0179]FIG. 30 shows the flow chart of the procedure carried out by thestack process (S313, S325, S335).

[0180] Referring to FIG. 30, one bin that is to be subjected to a stackoperation is selected at S401. More specifically, this is the bin towhich the printed sheet is output at step S313, the bin with theexceeded capacity in the stack process of S325, or the bin to which anout-of-range sheet is output in the stack process of S135.

[0181] At S403, transportation and stacking of a bundle of sheets fromthe selected bin to nonsort tray 20 is carried out. At S405,determination is made whether the sort mode is selected or not. When YESat S405, an operation of shifting the sheet output position is carriedout by a nonsort tray shift unit 20A shown in FIGS. 31 and 32. Then,determination is made whether there is another bin to be subjected to astack operation at S209. When YES at S209, the process from S201 isrepeated.

[0182] When NO at S405 or S409, control returns to the main routine.

[0183]FIG. 31 is a plan view to describe the shifting mechanism ofshifting the sheet discharge position of nonsort tray 20. The sheet isdischarged from a sheet discharge outlet 20B in the direction of “A” onnonsort tray 20. Nonsort tray shift unit 20A moves nonsort tray 20 inthe direction of “B”. After one bundle of sheets (or a bundle of sheetsfor one job) are discharged from sheet discharge outlet 20B, nonsorttray shift unit 20A moves nonsort tray 20 upwards in the drawing by apredetermined pitch. Then, a new bundle of sheets are discharged fromsheet discharge outlet 20B.

[0184] By repeating the above operation, bundle of sheets P1-P3 areplaced on nonsort tray 2.0 in respective offset positions. Therefore,the user can easily identify one bundle of sheets from another bundle ofsheets.

[0185] By the above processes, an operation set forth in the followingis realized.

[0186] [When Nonsort Mode is Selected]

[0187] (1) In a print operation, generally one bin is selected and asheet is output to that bin. A stack operation to the nonsort tray isnot carried out following the completion of the print operation (NO atS309).

[0188] (2) When the capacity of the bin is exceeded during a pintoperation, the sheet is transferred from that bin to the nonsort traywhen a stack operation is allowed (S325). Then, the output of a sheettowards the nonsort tray is resumed (S329). Accordingly, the sheets willnot be output in a diversed manner among the nonsort tray and the bin.

[0189] [When Sort Mode is Selected]

[0190] (1) A plurality of bins are selected in the print operation.Sheets are classified and output to these bins.

[0191] (2) When the print operation ends and a stack process is allowed,the sheet output to the bin is transferred to the nonsort tray to bestacked (S313). Here, the nonsort tray is shifted for each bin (S407).Therefore, the user can easily identify a bundle of sheets from anotherbundle of sheets.

[0192] (3) When the bin capacity is exceeded during a print operationand a stack process is allowed, the output to that bin is transferredand stacked to the nonsort tray (S325). Here, the nonsort tray isshifted for each bin (S407). Therefore, the user can easily identify abundle of sheets from another bundle of sheets.

[0193] Then, an empty bin is selected and output of a sheet towards thatbin is resumed (S319). When the output ends, the sheets are stacked(S313).

[0194] When a stack process cannot be carried out, a message can bedisplayed on touch panel 151 informing that the sheet output to the binby the resumed output is left in the bin, and the sorted sheets arestored in nonsort tray 20 and a particular bin in bin assembly 30.

[0195] [When Nonsort Mode or Sort Mode is Selected]

[0196] When a stack process is allowed in the event of a sheet thatcannot be output to the bin (for example, a sheet that is too great insize) is delivered, the sheet output to that bin is stacked at thenonsort tray (S335). Then, the subsequent output to that bin is carriedout towards the nonsort tray (S337). Accordingly, the process will notbe interrupted even when a sheet that cannot be output to the bin isdelivered. Also, the divided output of a sheet to a bin and to thenonsort tray can be prevented.

[0197] Although the present invention has been described and illustratedin detail, it is clearly understood that the same is by way ofillustration and example only and is not to be taken by way oflimitation, the spirit and scope of the present invention being limitedonly by the terms of the appended claims.

What is claimed is:
 1. A sheet processing device which processes sheetsdischarged from said image forming apparatus executing a print job,comprising: a first discharge tray, a plurality of second dischargetrays, a plurality of sensors which detect whether there is a sheet oneach of said plurality of second discharge trays, a transport unit whichtransports a bundle of sheets from said second discharge trays to saidfirst discharge tray, and a controller which controls said transportunit so that at least one of said second discharge trays is selectedaccording to a predetermined condition and a bundle of sheets aretransported from said selected second discharge tray for dischargingsheets by a new job when detection is made by said sensors of a sheet onall of said second discharge trays in discharging a sheet by a new job.2. The sheet processing device according to claim 1 , wherein saidpredetermined condition includes priority of a user requesting a job. 3.The sheet processing device according to claim 1 , wherein saidpredetermined condition includes the number of second discharge traysoccupied by a same job.
 4. The sheet processing device according toclaim 1 , wherein said predetermined condition includes the number ofsaid second discharge trays occupied by jobs requested by the same user.5. The sheet processing device according to claim 1 , wherein saidcontroller selects said second discharge tray located closest to saidfirst discharge tray.
 6. The sheet processing device according to claim1 , wherein said predetermined condition includes the number of sheetsdischarged to each said second discharge tray.
 7. The sheet processingdevice according to claim 1 , wherein said predetermined conditionincludes a size of a sheet discharged to each said second dischargetray.
 8. The sheet processing device according to claim 7 , wherein saidcontroller selects a second discharge tray storing a sheet of thelargest size.
 9. The sheet processing device according to claim 7 ,wherein said controller selects a second discharge tray upon comparisonbetween the size of a sheet discharged to said first tray and the sizeof a sheet discharged to each said second discharge tray.
 10. The sheetprocessing device according to claim 1 , wherein said predeterminedcondition includes whether a bundle of sheets discharged to each saidsecond discharge tray is stapled.
 11. The sheet processing deviceaccording to claim 1 , wherein said controller selects, when there is ajob that uses a number of second discharge trays identical in number tosaid second discharge trays that are to be used in a new job, saidsecond discharge tray used in said job.
 12. An image forming systemincluding a sheet processing device and an image forming apparatus, saidsheet processing device comprising: a first discharge tray, a pluralityof second discharge trays, a plurality of sensors which detect whetherthere is a sheet on each of said plurality of second discharge trays, atransport unit which transports a bundle of sheets from said seconddischarge trays to said first discharge tray, and a controller whichcontrols said transport unit so that at least one of said seconddischarge trays is selected according to a predetermined condition and abundle of sheets are transported from said selected second dischargetray for discharging sheets by a new job when detection is made by saidsensors of a sheet on all of said second discharge trays.
 13. The sheetprocessing device according to claim 1 , wherein said first dischargetray is provided above said second discharge trays.
 14. A sheetprocessing device comprising: a first discharge tray, a plurality ofsecond discharge trays, a plurality of sensors which detects whetherthere is a sheet on each of said plurality of second discharge trays, atransport unit which transports a bundle of sheets from said seconddischarge trays to said first discharge tray, and a controller whichcontrols a transport operation of said transport unit according to adetection result of said sensor.
 15. The sheet processing deviceaccording to claim 1 , wherein said controller provides control so as totransport by said transport unit from at least one second discharge trayselected according to a predetermined condition when detection is madeby said sensors of a sheet on all of said second discharge trays.
 16. Asheet processing device comprising: a first discharge tray, a pluralityof second discharge trays, a plurality of timers which count a period oftime of a bundle of sheets left on each of said plurality of seconddischarge trays, a transport unit which transports the bundle of sheetsdischarged on said second discharge tray to said first discharge tray,and a controller which controls a transport operation of said transportunit according to a counted result of said timers.
 17. The sheetprocessing device according to claim 16 , wherein said controllercontrols said transport unit so that a bundle of sheets are transportedfrom said second discharge tray having a count time exceeding apredetermined time by said timer.
 18. The sheet processing deviceaccording to claim 16 , further comprising a plurality of sensors whichdetect whether there are a bundle of sheets on each of said plurality ofsecond discharge trays, wherein said controller controls said transportunit so as to transport a bundle of sheets from a second discharge trayhaving a longest count time by said timer when detection is made of abundle of sheets on all of said second discharge trays.
 19. An imageforming system including a sheet processing device and an image formingapparatus, said sheet processing device comprising: a first dischargetray, a plurality of second discharge trays, a plurality of timers whichcount a period of time of a bundle of sheets left on each of saidplurality of second discharge trays, a transport unit which transportsthe bundle of sheets discharged on said second discharge tray to saidfirst discharge tray, and a controller which controls a transportoperation of said transport unit according to a counted result of saidtimers.
 20. A sheet processing device which processes sheets dischargedfrom said image forming apparatus executing a print job, comprising: amemory which stores identification information of a user requesting ajob corresponding to each job, a first discharge tray, a plurality ofsecond discharge trays, a transport unit which transports a bundle ofsheets discharged on said second discharge trays to said first dischargetray, and a controller which controls said transport unit so as totransport from said second discharge tray a bundle of sheets by aprevious job when a user of a new job differs from the user of theprevious job in discharging a sheet by the new job to said seconddischarge tray already storing a sheet by the previous job.
 21. Thesheet processing device according to claim 20 , further comprising astapler, wherein said controller controls said transport unit so as totransport a bundle of sheets by the previous job from said seconddischarge tray when the user of said new job is identical to the user ofsaid previous job, and a staple process is to be applied on the bundleof sheets by the new job.
 22. An image forming system including a sheetprocessing device and an image forming apparatus, said sheet processingdevice comprising: a memory which stores identification information of auser requesting a job corresponding to each job, a first discharge tray,a plurality of second discharge trays, a transport unit which transportsa bundle of sheets discharged on said second discharge trays to saidfirst discharge tray, and a controller which controls said transportunit so as to transport from said second discharge tray a bundle ofsheets by a previous job when a user of a new job differs from the userof the previous job in discharging a sheet by the new job to said seconddischarge tray already storing a sheet by the previous job.
 23. A sheetprocessing apparatus comprising: a first discharge tray, a plurality ofsecond discharge trays, a detector which detects that a sheet cannot bedischarged to at least one of said plurality of second discharge trays,a transport unit which transports a bundle of sheets discharged on saidsecond discharge trays to said first discharge tray, and a controllerwhich controls a transport operation of said transport unit according toa detected result of said detector.
 24. The sheet processing deviceaccording to claim 23 , wherein said detector detects a capacityoverflow state of the second discharge tray.
 25. The sheet processingdevice according to claim 24 , wherein said detector detects a sheetthat cannot be output to a second discharge tray.
 26. The sheetprocessing device according to claim 24 , wherein said controllercontrols said transport unit so that bundles of sheets are transportedfrom a plurality of said second discharge trays when said detectordetects said state, and resumes a discharge operation to a plurality ofsaid second discharge trays when said transportation ends.
 27. The sheetprocessing device according to claim 24 , wherein said controllercontrols said transport unit so as to transport bundles of sheets on aplurality of said second discharge trays after the resumed dischargeoperation ends.
 28. The sheet processing device according to claim 24 ,further comprising a display which displays presence of a bundle ofsheets on said first discharge tray and said plurality of seconddischarge trays after the resumed discharge operation ends.
 29. Thesheet processing device according to claim 26 , wherein said first trayincludes a shift mechanism to shift a sheet, said sheet shift mechanismshifting a discharge position for each bundle of sheets transported bysaid transport unit.
 30. The sheet processing device according to claim23 , wherein said controller controls said transport unit so as totransport a bundle of sheets on a second discharge tray detected of saidstate when said detector detects said state, and resumes a dischargeoperation to said first tray when transportation ends.
 31. An imageforming system including a sheet processing device and an image formingapparatus, said sheet processing device comprising: a first dischargetray, a plurality of second discharge trays, a detector which detectsthat a sheet cannot be discharged to at least one of said plurality ofsecond discharge trays, a transport unit which transports a bundle ofsheets discharged on said second discharge trays to said first dischargetray, and a controller which controls a transport operation of saidtransport unit according to a detected result of said detector.
 32. Asheet discharge method in a sheet processing device including atransport unit transporting a bundle of sheets from a plurality ofsecond discharge trays to a first tray, said method comprising the stepsof: discharging sheets to a plurality of said second discharge trays,determining whether there are a bundle of sheets on each tray of saidplurality of second discharge trays, selecting at least one of saidsecond discharge trays according to a predetermined condition when abundle of sheets are detected at all of said second discharge trays,transporting a bundle of sheets from said selected second discharge trayto said first tray, and discharging a new bundle of sheets to saidselected second discharge tray after said transportation step ends. 33.A sheet discharge method of a sheet processing device including atransport unit transporting a bundle of sheets from a plurality ofsecond discharge trays to a first tray, said method comprising the stepsof: discharging sheets to a plurality of second discharge trays,counting a period of time of a bundle of sheets left on each said seconddischarge tray, selecting at least one second discharge tray accordingto said time count result, transporting a bundle of sheets from saidselected second discharge tray to said first tray, and discharging a newbundle of sheets to said selected second discharge tray after saidtransportation step ends.
 34. A sheet discharge method of a sheetprocessing device including a transport unit transporting a bundle ofsheets from a plurality of second discharge trays to a first tray, saidmethod comprising the steps of: selecting at least one second dischargetray from a plurality of second discharge trays, discharging a firstbundle of sheets to said selected second discharge tray, determiningwhether a second bundle of sheets correspond to a user of said firstbundle of sheets, transporting the first bundle of sheets from saidsecond discharge tray to said first tray when determination is made ofthe same user, and discharging the second bundle of sheets to saidselected second discharge tray after the end of transportation.
 35. Asheet discharge method of a sheet processing device including atransport unit transporting a bundle of sheets to a first tray from aplurality of second discharge trays, said method comprising the stepsof: selecting at least one second discharge tray from a plurality ofsecond discharge trays, discharging a bundle of sheets to said selectedsecond discharge tray, detecting a state of not being able to dischargea sheet to at least one of said selected second discharge tray, andtransporting a bundle of sheets from said selected second discharge trayto said first tray when said state is detected.